Quaternary Arsenides <i>AM</i><sub>1.5</sub><i>Tt</i><sub>0.5</sub>As<sub>2</sub> (<i>A</i> = Na, K, Rb; <i>M</i> = Zn, Cd; <i>Tt</i> = Si, Ge, Sn): Size Effects in CaAl<sub>2</sub>Si<sub>2</sub>- and ThCr<sub>2</sub>Si<sub>2</sub>-Type Structures
Bibliographic record
Abstract
Ten quaternary arsenides AM(1.5)Tt(0.5)As2 (A = Na, K, Rb; M = Zn, Cd; Tt = Si, Ge, Sn) have been prepared by stoichiometric reactions of the elements at 600-650 °C. Seven of them (NaZn(1.5)Si(0.5)As2, NaZn(1.5)Ge(0.5)As2, NaZn(1.5)Sn(0.5)As2, NaCd(1.5)Sn(0.5)As2, KZn(1.5)Sn(0.5)As2, KCd(1.5)Sn(0.5)As2, RbCd(1.5)Sn(0.5)As2) adopt the trigonal CaAl2Si2-type structure (Pearson symbol hP5, space group P3m1, Z = 1, a = 4.0662(3)-4.4263(7) Å, c = 7.4120(5)-8.4586(14) Å), whereas the remaining three (KZn(1.5)Si(0.5)As2, KZn(1.5)Ge(0.5)As2, RbZn(1.5)Ge(0.5)As2) adopt the tetragonal ThCr2Si2-type structure (Pearson symbol tI10, space group I4/mmm, Z = 2, a = 4.0613(10)-4.1157(5) Å, c = 14.258(3)-14.662(2) Å). Both structure types contain anionic [M(1.5)Tt(0.5)As2] slabs that are built from edge-sharing tetrahedra and that stack alternately with nets of A cations. A structure map delineates the formation of these structure types for AM(1.5)Tt(0.5)As2 as a function of simple radius ratios. Although these arsenides have charge-balanced formulations, band structure calculations on NaZn(1.5)Tt(0.5)As2 (Tt = Si, Ge, Sn) indicate that semimetallic behavior is predicted as a result of overlap of the valence and conduction bands.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".